The present invention relates to an electrostatographic printing machine, and relates more particularly to an active airflow system therein for containing, transporting, and purging particulate contaminants therefrom.
In an electrostatographic imaging device, the following general process is implemented. A photoconductive member is first charged to a substantially uniform potential. The charge carrying surface of the photoconductive member is then exposed to a light image of a document. The charge on selective areas of the photoconductive member is dissipated by the light image. This results in an electrostatic image being recorded on the photoconductive member, which corresponds to the document being reproduced. The electrostatic image is subsequently developed into a visible image by depositing a charged developing material onto the photoconductive member. The developing materials, e.g., toner particles, are attracted to the charged image areas on the photoconductive member. This attraction creates a toner image on the photoconductive member, which is then permanently affixed to a copy sheet.
When multicolor electrostatographic printing is desired, a similar process is executed. In black and white printing, a single image is formed on the photoconductive member in order to reproduce a document. In multicolor electrostatographic printing, multiple images corresponding to different colors are individually recorded on the photoconductive member. Then each electrostatographic image is developed with toner of a single complementary color, and the process is repeated for different colored images and respective different colored toner. Subsequently, each single color toner image is transferred to the copy sheet in superimposed registration with the prior toner image. This creates a multilayered toner image on the copy sheet. The multilayered toner image is permanently affixed to the copy sheet.
In electrostatographic printing, some development systems utilize two component developer mixes or single component developer materials as well as powder or liquid developer materials. In the two component developer mix, the dyed or colored thermoplastic powder is combined with coarser ferromagnetic granules. The thermoplastic powder, otherwise known as toner particles, and the ferromagnetic granules, otherwise known as carrier beads, are selected to ensure that the toner particles acquire a desired electrostatic charge relative to the electrostatic image recorded on the photoconductive member. As the developer mix is brought into contact with the charged photoconductive member, the larger attractive force of the electrostatic image recorded on the photoconductive member causes the toner particles to transfer from the carrier beads to the electrostatic image.
In order to control toner deposition, known development systems utilize rotary impellers, fur brushes, bucket conveyors and magnetic brush systems. Of these systems, the magnetic brush system has proven more effective. Such a system includes a developer roll with a directional magnetic flux field, which promotes contact between the developer mix and the photoconductive member.
One issue associated with the aforementioned developing process is the unintentional or inadvertent escape of developing material, specifically liquid or dry toner particles, from the developer housing. Toner particles that carry an electrostatic charge are readily attracted to various surfaces within the electrostatographic printing machine. This attraction can result in the contamination of various machine components. Further, because of the charge on the toner particles, escaping toner particles can be developed on the photoreceptor, which produces a background image on the reproduction of the document. Such contamination caused by floating toner particles adversely affects the performance and reliability of the electrostatographic printing machine. As a further example, developing material such as toner particles can collect on, e.g., a lamp, a mirror, a lens, etc. Such occurrences generate unacceptable copy quality as well as unscheduled and more frequent maintenance and repair visits by service technicians.
In multi-color electrostatographic printing machines, the escape of toner particles can cause intermingling of different color toner particles, which in turn causes contamination of the development system. It is therefore desirable to prevent the escape of toner particles and other particulate matter from each developer housing to prevent the contamination of the development system.
To address the issue of toner particle escape, one of ordinary skill in the art can appreciate that a developer housing can include a seal or other physical barrier to prevent the escape or migration of the toner particles outside of the developer housing. In addition, one can appreciate that a developer housing can be maintained at a negative pressure relative to the ambient environment of the electrostatographic printing machine. This generates an inner flow through a duct system, which transports toner particles and other particulate matter out of the developer housing. Typically, the duct systems or ductwork networks include ducts, which direct the airflow into a filter or other depository area.
One issue associated with the negative pressure ductwork network solution is that typically such systems require a significant bulk airflow. The majority of the airflow is required to maintain adequate particulate matter transport velocities to minimize contaminant deposition throughout the ductwork network. In a four housing full color system, the total bulk flow requirement for the development subsystem becomes 60 ft3/min. When combined with the bulk airflow requirements of other subsystems, such as the cleaner (50 ft3/min) and hybrid air knife (25 ft3/min) subsystems, the blower system requirements can exceed 135 ft3/min, which exceeds desired product performance levels for cost, power, and noise.
For the foregoing reasons, there exists in the art a need for an image forming system, such as an electrostatographic printing system, having a ductwork network cleaning system that adequately transports toner particles and particulate matter through the ductwork network as desired without exceeding product performance levels for cost, power, and noise. The present invention is directed toward further solutions in this art.
In accordance with one aspect of the present invention, an image forming system is provided having a ductwork network for passing, or transporting, a fluid and particulate matter therethrough. The system also includes at least one fluid regulating element coupled to the ductwork network and to one or more subsystems of the image forming system. The fluid regulating element regulates fluid flow through the ductwork network. Also provided is a fluid displacement device, in fluid communication with the ductwork network for displacing fluid within the ductwork network. Most commonly, the fluid contained within the image forming system is air.
According to one aspect of the present invention, the fluid regulating element comprises a shutoff valve.
According to another aspect of the present invention, the fluid displacement device comprises a blower. The blower creates a pressure (negative or positive) within the ductwork network to displace the fluid, e.g., air, within the ductwork network and to transport the particulate matter through the system.
According to still another aspect of the present invention, a method is provided for cleaning the ductwork network in the image forming system. The method includes activating the fluid displacement device to establish a selected fluid pressure and create a fluid flow within at least a portion of the ductwork network. Such fluid pressure transports particulate matter through the ductwork network. The method further includes purging sections of the ductwork network by activating at least one fluid regulating element within the ductwork network. Such purging diverts fluid flow and generates an increased fluid flow level through sections of the ductwork network being purged, which transports an additional amount of particulate matter through the ductwork network. According to still neither aspect of the present invention, the purging step includes purging the ductwork network during one of a cycle-up, cycle-down, or dead cycle system state.